1. Field of the Invention
The present invention relates to a sewing machine and a control method for driving the sewing machine, and more particularly to a sewing machine and a control method for driving the sewing machine having a rotatable head portion in order to implement a perfect sewing operation without a hitch stitch when sewing an airbag, a bag, shoes or the like.
2. Description of the Prior Art
As generally known in the art, a workpiece or object to be sewn (referred to as a “sewing object” hereinafter) such as an airbag, a bag, shoes or the like is thick as well as has a number of sewing lines with delicate patterns to be sewn like a circular, curved or inclined line, etc. The conventional sewing machine has left a hitch stitch due to a sewing direction, which leads to drawbacks in that the stitch pattern becomes irregular to lower the quality of the sewing object.
FIG. 1 shows one example of the conventional sewing machine in which an arm portion 40 including a head portion is positioned above a table 10, and a bed portion (not shown) including a hook is disposed under the table 10. A coupling portion 60 is configured to connect the arm portion 40 with the bed portion. Hence, the head portion and the hook of the bed portion are adapted to cooperate to sew the sewing object which is fixedly held at a sewing object fixing member 50.
The sewing machine constructed above is capable of processing the sewing object in a restricted region in which the sewing object fixing member 50 is allowed to move in an X-axis or Y-axis direction with the structure of the arm-bed portions.
However, this conventional sewing machine has drawbacks in that a hitch stitch occurs between the respective stitches when performing a circular, curved or inclined stitch since the sewing object fixing member 50 linearly moves in the X-axis or Y-axis direction.
FIGS. 2A and 2B show examples where a hitch stitch occurs in the conventional sewing machine. In the case of a rhombic or rectangular pattern, it will be noted that two sides out of four sides refer to a P stitch of a perfect stitch, one side refers to an H/P stitch mixed with normal and abnormal stitches, and one side refers to an H stitch of a hitch stitch.
FIG. 2C illustrates an H-P stitch distribution between the respective stitches after a sewing operation. It will be appreciated that the P stitch (a perfect stitch) and an H stitch (a hitch stitch) occur approximately at a 1:1 ratio for a circular stitch.
Hence, there has been a need to provide a sewing machine which may implement a perfect stitch with respect to the entire stitches for a high quality sewing operation.
Meanwhile, in the case that the size of the sewing object increases, the sewing machine needs to be large due to the restriction of the sewing operation region. Hence, it has been requested to develop a sewing machine having a new concept to minimize an installation space of a large pattern sewing machine.